1. Field of the Invention
The present invention relates to a two-component type polyurethane composition, a two-component type micro foamed polyurethane elastomer, applications thereof and a process of preparing the same. In particular, the present invention relates to a two-component type polyurethane composition and a two-component type micro foamed polyurethane elastomer both excellent in sag resistance, a process of preparing the same, a polyurethane sealant for sealing joints in buildings, doors and the like, and in bodies of cars, and a process of preparing the same.
2. Background of the Invention
Due to their excellent physical properties such as rubber elasticity, cold proof resistance and durability, polyurethane resins have been lately used as sealing materials for buildings, cars, etc. The sealing materials for use in buildings and cars are required to be applicable to the base surface of a variety of shapes. And it is particularly important for them to have such excellent sag resistance that they do not sag down while being applied to a vertical or sloping surface even to enough thickness to exhibit watertightness.
Thus, in order to prevent the fluid from sagging, mineral fillers such as surface treated calcium carbonate, colloidal silica and bentonite, which have been treated with higher fatty acid or fatty ester, or organic matter such as hydrogenated castor oil, aliphatic amide wax or polytetrafluoroethylene resin (PTFE) have been generally added to the polyurethane resins as thixotropy-imparting agent (thixotropic agent).
The use of these thixotropic agents, however, causes problems that, since a large amount of such agents must be add to the polyurethane resins so as to enhance the sag resistance, apparent viscosity of the polyurethane resins increases at the time of their application, and hence workability is deteriorated and that the resins with such agents are often poor in storage stability.
The use of amines, as thixotropic agents, has been also well known. For example, there is disclosed in Japanese Patent Publication No. 54-26274 a method of preparing a polyurethane elastomer which is characterized by reacting a polyisocyanate component and polyoxyalkylene polyamine. And there is disclosed in Japanese Patent Publication No. 53-4527 a method of preparing an adhesive based on polyurethane composed of an isocyanate-terminated prepolymer, a polyhydroxy compound and a catalyst in which part of the polyhydroxy compound is substituted with a primary amine compound having a chemical formula R(NH2)n (wherein R represents an aliphatic hydrocarbon group having 8 or less carbon atoms, n=2 to 4) in an amount of 4 to 30% by equivalent weight based on the free isocyanate group content of prepolymer.
Each of these methods, however, has a problem that it takes several seconds to several minutes from the moment of mixing a polyisocyanate component and active hydrogen component of amine, etc. to the moment of the development of thixotropy. Thus, although they are applicable in the case of hand-application with a caulking gun or mechanical-application with a low-pressure apparatus, they have no practical use in the case of application with a high-pressure apparatus which requires higher working efficiency, because it takes them too much time to allow the development of thixotropy to take place.
In such a situation, there have been demands that sealing materials should appear which enable more excellent development of thixotropy and have more excellent physical properties, thereby are applicable under various conditions such as mechanical-application, hand-application and application with a high-pressure apparatus.
In light of the above problems, the present inventors concentrated their energies on studying a two-component type polyurethane composition in which development of excellent thixotropy takes place immediately after mixing a polyisocyanate component and active hydrogen compound component. And the present inventors finally found that, for the two-component type polyurethane composition or the two-component type micro foamed polyurethane elastomer obtained from a polyisocyanate component and active hydrogen compound component, when using an alicyclic diamine as active hydrogen compound, it develops such excellent thixotropy that it is applicable under various conditions such as mechanical-application, hand-application, etc. even if it substantially contains no thixotropic agents, because the alicyclic diamine participates in the development of thixotropy, and that the above composition or elastomer has excellent sag resistance and other physical properties. The present inventors also found that the above composition or elastomer is suitable for sealing material, which led to the completion of the present invention.
The present invention was made to solve the problems attendant to the prior arts as described above, and the object of the present invention is to provide a two-component type polyurethane composition and a two-component type micro foamed polyurethane elastomer which develop excellent thixotropy immediately after mixing a compound having an isocyanate group and a compound having active hydrogen, enable their application under various conditions such as mechanical-application, hand-application, etc, and in addition, have excellent sag resistance and other physical properties suitable for sealing materials, and a method of preparing the same.
The two-component type polyurethane composition according to the present invention is obtained from a principal component containing a compound having an isocyanate group and a curing agent containing a compound having active hydrogen and is characterized in that both the above principal component and the above curing agent contain substantially no thixotropic agent, the total time from the moment of mixing the above principal component and the above curing agent to the moment of the development of thixotropy is 2 seconds or shorter, the slump of the mixture of the above principal component and the above curing agent is 3 mm or smaller, the above compound having active hydrogen has flash point of 60xc2x0 C. or higher, and that, when boiling the cured two-component type polyurethane composition in boiling water under atmospheric pressure for 60 minutes, change in mass of the above cured two-component type polyurethane composition before and after the boiling is 0.6% or smaller by mass.
Preferably the two-component type polyurethane composition described above has break strength of not less than 0.5 MPa and not more than 30 MPa at xe2x88x9230xc2x0 C. and elongation at break of not less than 50% and not more than 700% at xe2x88x9230xc2x0 C. Preferably the compound having active hydrogen described above has at least two hydroxyl groups and/or at least two amino groups.
Preferably the two-component type polyurethane composition described above has a constitutional unit having the following general formula [I]: 
wherein m, n represent an integer from 1 to 5 independently, in the rate of not less than 0.001% and not more than 30% by mass.
Preferably the compound having active hydrogen described above contains alicyclic diamine.
Preferably the above alicyclic diamine is polycyclic aliphatic diamine having the following general formula [II]: 
wherein m, n represent an integer from 1 to 5 independently.
Preferably the above alicyclic diamine content of the compound having active hydrogen described above is not less than 1% and not more than 50% by equivalent weight as active hydrogen group conversion on the basis of the total active hydrogen group in the same compound.
The two-component type micro foamed polyurethane elastomer according to the present invention is obtained from a principal component containing a compound having an isocyanate group, a curing agent containing a compound having active hydrogen and a foaming agent and is characterized in that both the above principal component and the above curing agent contain substantially no thixotropic agent, the total time from the moment of mixing the above principal component, the above curing agent and the above foaming agent to the moment of the development of thixotropy is 2 seconds or shorter, the slump of the mixture of the above principal component, the above curing agent and the above foaming agent is 3 mm or smaller, the above compound having active hydrogen has flash point of 60xc2x0 C. or higher, and that, when boiling the cured two-component type micro foamed polyurethane elastomer in boiling water under an atmospheric pressure for 60 minutes, change in mass of the above cured two-component type polyurethane elastomer before and after the boiling is 0.6% or smaller by mass. Preferably, the above two-component type micro foamed polyurethane elastomer has a total density of 100 to 900 kg/m3 and the average diameter of its cells is 1 to 100 xcexcm.
Preferably the two-component type micro foamed polyurethane elastomer described above has a constitutional unit having the following general formula [I]: 
wherein m, n represent an integer from 1 to 5 independently, in the rate of not less than 0.001% and not more than 30% by mass.
Preferably the compound having active hydrogen described above contains alicyclic diamine.
Preferably the above alicyclic diamine is polycyclic aliphatic diamine having the following general formula [II]: 
wherein m, n represent an integer from 1 to 5 independently.
The process of preparing the two-component type polyurethane composition according to the present invention is characterized by using a principal component containing a compound having an isocyanate group, a curing agent containing alicyclic diamine.
The polyurethane sealant according to the present invention is characterized by containing the above two-component type polyurethane composition or the above two-component type micro foamed polyurethane elastomer.
The process of preparing the polyurethane sealant according to the present invention is characterized by using the above two-component type polyurethane composition or the above two-component type micro foamed polyurethane elastomer.
The two-component type polyurethane composition or the two-component type micro foamed polyurethane elastomer according to the present invention is obtained by mixing a principal component containing a compound having an isocyanate group and a curing agent containing a compound having active hydrogen (hereinafter sometimes referred to as xe2x80x9cactive hydrogen compoundxe2x80x9d) such as alicyclic diamine, etc. The curing agent generally contains polyol, and both of the principal component and the curing agent may contain other additives according to situations.
The two-component type polyurethane composition, the two-component type micro foamed polyurethane elastomer and the process of preparing the same will be described in further detail.
The two-component type polyurethane composition according to the present invention is obtained from a principal component (A) containing a compound having an isocyanate group and a curing agent (B) containing a compound having active hydrogen, and both the above principal component (A) and the above curing agent (B) contain substantially no thixotropic agent.
The two-component type polyurethane composition according to the present invention develops thixotropy after mixing the above principal component and the above curing agent. The total time immediately after the moment of mixing the above principal component and the above curing agent to the development of thixotropy is 2 seconds or shorter, preferably 1.5 seconds or shorter, and more preferably 1 seconds or shorter.
The slump of the mixture of the above principal component and the above curing agent is 3 mm or smaller, preferably 2 mm or smaller, and more preferably 1 mm or smaller.
The above compound having active hydrogen has flash point of 60xc2x0 C. or higher, preferably 65xc2x0 C. or higher, and more preferably 70xc2x0 C. or higher.
When boiling the above two-component type polyurethane composition, which is obtained by curing the above mixture, in boiling water under an atmospheric pressure for 60 minutes, change in mass of the above two-component type polyurethane composition before and after the boiling is 0.6% or smaller by mass, preferably 0.55% or smaller by mass.
The term xe2x80x9csubstantially contain no thixotropic agentxe2x80x9d used herein means that the content of the compounds having the function of thixotropic agents, other than the compound having an isocyanate group and the compound having active hydrogen both of which participate in the formation of urethane bond of the process of the two-component type polyurethane composition or the two-component type micro foamed polyurethane elastomer of the invention, in the two-component type polyurethane composition or the two-component type micro foamed polyurethane elastomer is 0.001% or smaller by mass of the whole two-component type polyurethane composition or the whole two-component type micro foamed polyurethane elastomer.
For the two-component type polyurethane composition according to the present invention, desirably its break strength at xe2x88x9230xc2x0 C. is preferably not less than 0.5 MPa and not more than 30 MPa and more preferably not less than 1.0 MPa and not more than 25 MPa. Further, for the two-component type polyurethane composition according to the present invention, desirably its elongation at break at xe2x88x9230xc2x0 C. is preferably not less than 50% and not more than 700% and more preferably 600% or smaller.
Desirably the two-component type polyurethane composition according to the present invention has a constitutional unit having the following general formula [I]: 
wherein m, n represent an integer from 1 to 5 independently, in the rate of not less than 0.001% and not more than 30% by mass and preferably in the rate of not less than 0.005% and not more than 25% by mass.
The two-component type polyurethane composition according to the present invention is composed of the above principal component (A) containing a compound having an isocyanate group and the above curing agent (B) containing a compound having active hydrogen and can be prepared by mixing the above principal component (A) and the above curing agent (B) by conventional mixing procedure.
 less than Principal Component (A) greater than 
The compounds having an isocyanate group, which are contained in the principal component (A) used in the present invention, are generally organic compounds having an isocyanate group, and such organic compounds include, for example, aromatic isocyanate, aliphatic isocyanate, alicyclic isocyanate, the mixture thereof, or modified organic isocyanate compounds such as urethane prepolymer, etc.
Of all the above organic compounds, preferably used are urethane prepolymers having isocyanate group ends which are obtained by reacting a polyisocyanate compound having two or more isocyanate groups in a molecule or a polyisocyanate having two or more molecular end isocyanate groups in a molecule with an active hydrogen compound under the stoichiometrically excessive conditions.
(Compound Having Isocyanate Group (Isocyanate))
The compounds having an isocyanate group used in the principal component may be isocyanates used in conventional polyurethane resin compositions. Preferably used are polyisocyanates having 2 or more molecular end isocyanate groups per molecular.
The compounds having isocyanate-groups include, for example, aromatic isocyanates such as tolylene diisocyanate (TDI), hydrogenated tolylene diisocyanate, diphenylmethane diisocyanate (MDI), polymeric MDI (PMDI), xylylene diisocyanate (XDI) and 1,5-naphthalene diisocyanate (NDI); aliphatic isocyanates such as hexamethylene diisocyanate (HDI); alicyclic polyisocyanates such as isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI) and methyl norbornane diisocyanate (NBDI); carbodiimide modified isocyanates of the above isocyanates; and modified isocyanurates, etc.
Of all the above compounds, in terms of reactivity, preferably used are TDI, MDI, carbodiimide modified MDI (fluid MDI) and PMDI.
The compounds having isocyanate groups may be used solely or in the form of mixture of two or more kinds.
(Active Hydrogen Compound used for Preparing Urethane Prepolymer)
The active hydrogen compounds used for preparing the above urethane prepolymer may be those used for preparing conventional polyurethane resin compositions obtained from an isocyanate and active hydrogen compounds such as polyol.
To be concrete, the active hydrogen compounds are compounds having active hydrogen reactive with isocyanates, such as polyols (compounds having two or more hydroxyl groups at its ends) and diamine compounds.
The above polyols include, for example, polyhydric alcohols having relatively low-molecular weight, polyether polyols, polyester polyols, or modified polyether polyols and polyester polyols.
To be more concrete, the polyhydric alcohols having relatively low-molecular weight include, for example, dihydric alcohols such as ethylene glycol (EG), diethylene glycol (DEG), propylene glycol (PG), dipropylene glycol (DPG), 1,3-butanediol (1,3-BD), 1,4-butanediol (1,4-BD), 4,4xe2x80x2-dihydroxyphenylpropane and 4,4xe2x80x2-dihydroxyphenylmethane; trihydric alcohols such as glycerol, 1,1,1-trimethylolpropane (TMP), 1,2,5-hexanetriol; and polyhydric alcohols having four or more hydroxyl groups in a molecule such as pentaerythritol, glucose, sucrose and sorbitol.
The polyether polyols include, for example, polyether polyols obtained by the addition polymerization of one kind or more kinds of polyhydric alcohols having relatively low-molecular weight and one kind or more kinds of oxides selected from the group consisting of ethylene oxide, propylene oxide, butylenes oxide, etc., and poly(tetramethylene ether) glycol (PTMEG) obtained by the ring-opening polymerization of tetrahydrofuran.
The polyester polyols include, for example, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, glycerol, trimethylolpropane, in addition, polyester polyols obtained by the condensation polymerization of at least one kind of other low-molecular weight polyols and at least one kind of acids selected from the group consisting of glutaric acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acids, or other low-molecular dicarboxylic acids and oligomer acids, and polyester polyols obtained by the ring-opening polymerization of caprolactone, etc.
The modified polyether polyols or polyester polyols include, for example, polymer polyols obtained by the graft polymerization of the above described well-known polyether polyols or polyester polyols and ethylenic unsaturated compounds such as acrylonitrile, styrene and methyl methacrylate.
The diamine compounds include, for example, aliphatic diamines such as ethylenediamine and aromatic diamines.
Of all the above described active hydrogen compounds, polyols are preferable. In terms of low viscosity of materials and improvement in water resistance of the sealant to be obtained, relatively low-molecular weight polyhydric alcohols and polyether polyols are more preferable.
These active hydrogen compounds can be used solely or in combination with two or more kinds.
(Method of Synthesizing Urethane Prepolymer)
The methods of synthesizing urethane prepolymer are not limited to any specific ones. Urethane prepolymer can be obtained, for example, following the procedure of: mixing isocyanate in excess of that stoichiometrically required and an active hydrogen compound at a time, or preparing any one of them first, then adding the other one thereto; and allowing them to react with each other at 10 to 120xc2x0 C. for 1 to 150 hours. The reaction may be allowed to proceed using well-known catalysts so as to enhance the reaction rate.
The curing agent (B) according to the present invention contains a compound having active hydrogen. The active hydrogen compound has flash point of 60xc2x0 C. or higher, as described above, and generally contains polyamine having two or more amino groups in a molecule and/or polyol having two or more hydroxyl groups in a molecule. The curing agent (B) may contain chain extender, catalysts, etc. according to situations. The use of the active hydrogen compound having flash point of 60xc2x0 C. or higher enables the operation of the two-component type polyurethane composition to be easier when using it on a building site, etc., moreover, it enables the suppression of odor; thereby the good working environment can be easily maintained on site.
The curing agent (B) can be preferably used as a sealing material by optionally mixing it with additives such as filler, plasticizer, age resister, ultraviolet absorber, light stabilizer, anti oxidant, coloring materials such as pigment and dye, and dispersant.
The curing agent (B) can be used as a foam sealing material by the addition of foam stabilizer and foaming agent. Part of or the whole amount of these and other additives to be mixed may be added to the principal component as long as their addition does not deteriorate the effects of the present invention.
 less than Polyol greater than 
The polyols used in the curing agent (B) may be the same as or different from those used in the urethanepolymer of the above described principal component (A).
The polyols include, for example, polyhydric alcohols having relatively low-molecular weight, polyether polyols, polyester polyols, caprolactone polyols, polycarbonate polyols, or modified polyether polyols and polyester polyols.
These polyols can be used solely or in the form of the mixture of two or more kinds.
(Polyhydric Alcohol)
To be more concrete, the polyhydric alcohols having relatively low-molecular weight include, for example, dihydric alcohols such as ethylene glycol (EG), diethylene glycol (DEG), propylene glycol (PG), dipropylene glycol (DPG), 1,3-butanediol (1,3-BD), 1,4-butanediol (1,4-BD), 4,4xe2x80x2-dihydroxyphenylpropane and 4,4xe2x80x2-dihydroxyphenylmethane; trihydric alcohols such as glycerol, 1,1,1-trimethylolpropane (TMP), 1,2,5-hexanetriol; and polyhydric alcohols having four or more hydroxyl groups in a molecule such as pentaerythritol, glucose, sucrose and sorbitol.
(Polyether Polyol)
The polyether polyols include, for example, polyether polyols obtained by the addition polymerization of at least one kind of polyhydric alcohols having relatively low-molecular weight and at least one kind of oxides selected from the group consisting of ethylene oxide, propylene oxide, butylenes oxide, etc., and poly(tetramethylene ether) glycol (PTMEG) obtained by the ring-opening polymerization of tetrahydrofuran.
(Polyester Polyol)
The polyester polyols include, for example, polyester polyols obtained by the condensation polymerization of at least one kind of polyols selected from the group consisting of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, glycerol, trimethylolpropane, etc. or other low-molecular weight polyols and at least one kind of acids selected from the group consisting of glutaric acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acids, etc. or other low-molecular weight dicarboxylic acids and oligomer acids, and polyester polyols obtained by the ring-opening polymerization of caprolactam, etc.
(Polycaprolactone Polyol)
The polycaprolactone polyols applicable to the present invention are the polyols obtained from xcex5-caprolactone and polyhydric alcohol, and generally those having number-average molecular weight of 500 to 4000 and hydroxyl value of about 30 to 240 mgKOH/g are preferable. As polyhydric alcohols, those used in the above described polyester polyols can be used.
(Polycarbonate Polyol)
The polycarbonate polyols applicable to the present invention are straight-chain aliphatic diols obtained by the condensation reaction of the polyhydric alcohols, such as 1,4-butanediol and 1,6-hexanediol, and the carbonates, such as dimethyl carbonate and diethyl carbonate, and generally those having hydroxyl value of about 60 to 200 mgKOH/g are preferable.
(Modified Polyether Polyol or Polyester Polyol)
The modified polyether polyols or polyester polyols include, for example, the polymer polyols obtained by the graft polymerization of the above described known polyether polyols or polyester polyols and ethylenic unsaturated compounds such as acrylonitrile, styrene and methyl methacrylate.
When using these modified polyether polyols or polyester polyols as active hydrogen compounds, their amount used may be properly set according to the objects of their physical properties; generally and desirably the amount is 5 to 250 parts by mass per 100 parts of the principal component (A), preferably 10 to 220 parts by mass.
(Polymer Polyol)
The polyether polyols according to the present invention may be used as polymer polyols. These polymer polyols are the vinyl polymer particle dispersing polyols obtained by the dispersion polymerization of ethylenic unsaturated group containing monomers, such as acrylonitrile and styrene, in polyether polyol using free-radical initiator such as azobisisobutyronitrile. Desirably the polymer content of the polyether polyol is 2 to 50% by mass, preferably about 10 to 40% by mass. Preferably the polymer polyols contain at least 30% styrene, as a vinyl polymer, by mass, preferably 35% or more styrene by mass.
(Alicyclic Diamine)
As polyamines used in the curing agent (B) according to the present invention, preferably used are alicyclic diamines. The alicyclic diamines include, for example, 2,5(6)-diaminomethylbicyclo[2,2,1]heptane, 2-aminomethyl-5(6)-aminoethylbicyclo[2,2,1]heptane, 2-aminomethyl-5(6)-aminopropylbicyclo[2,2,1]heptane, 2-aminomethyl-5(6)-aminobutylbicyclo[2,2,1]heptane, 2-aminomethyl-5(6)-aminopentylbicyclo[2,2,1]heptane, 2,5(6)-diaminoethylbicyclo[2,2,1]heptane, 2,5(6)-diaminopropylbicyclo[2,2,1]heptane, 2,5(6)-diaminobutylbicyclo[2,2,1]heptane, 2,5(6)-diaminopentylbicyclo[2,2,1]heptane, 5(6)-diaminomethylbicyclo[2,2,2]octane, 2-aminomethyl-5(6)-aminoethylbicyclo[2,2,2]octane, 2-aminomethyl-5(6)-aminopropylbicyclo[2,2,2]octane, 2-aminomethyl-5(6)-aminobutylbicyclo[2,2,2]octane, 2-aminomethyl-5(6)-aminopentylbicyclo[2,2,2]octane, 2,5(6)-aminoethylbicyclo[2,2,2]octane, 2,5(6)-diaminopropylbicyclo[2,2,2]octane, 2,5(6)-diaminobutylbicyclo[2,2,2]octane, 2,5(6)-diaminopentylbicyclo[2,2,1]octane, 3(4),8(9)-diaminomethyltricyclo[5,2,1,02,6]decane, 3(4)-aminomethyl-8(9)-aminoethyltricyclo[5,2,1,02,6]decane, 3(4)-aminomethyl-8(9)-aminopropyltricyclo[5,2,1,02,6]decane, 3(4)-aminomethyl-8(9)-aminobutyltricyclo[5,2,1,02,6]decane, 3(4)-aminomethyl-8(9)-aminopentyltricyclo[5,2,1,02,6]decane, 3(4),8(9)-diaminoethyltricyclo[5,2,1,02,6]decane, 3(4),8(9)-diaminopropyltricyclo[5,2,1,02,6]decane, 3(4),8(9)-diaminobutyltricyclo[5,2,1,02,6]decane, 3(4),8(9)-diaminopentyltricyclo[5,2,1,02,6]decane, 3(4),7(8)-diaminomethylbicyclo[4,3,01,6]nonane, 3(4)-aminomethyl-7(8)-aminoethylbicyclo[4,3,01,6]nonane, 3(4)-aminomethyl-7(8)-aminopropylbicyclo[4,3,01,6]nonane, 3(4)-aminomethyl-7(8)-aminobutylbicyclo[4,3,01,6]nonane, 3(4)-aminomethyl-7(8)-aminopentylbicyclo[4,3,01,6]nonane, 3(4),7(8)-diaminoethylbicyclo[4,3,01,6]nonane, 3(4),7(8)-diaminopropylbicyclo[4,3,01,6]nonane, 3(4),7(8)-diaminobutylbicyclo[4,3,01,6]nonane, 3(4),7(8)-diaminopentylbicyclo[4,3,01,6]nonane, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, and 1,4-diaminocyclohexane. These alicyclic diamines can be used solely or in the form of the mixture of two or more kinds.
Of all the above described alicyclic diamines, preferably used are polycyclic aliphatic diamines having the following general formula [II]: 
wherein m, n represent an integer from 1 to 5 independently.
It is considered that these alicyclic diamines impart thixotropy to the two-component type polyurethane composition obtained.
Desirably the alicyclic diamine content of the active hydrogen compounds is not less than 1% and not more than 50% by equivalent weight, preferably not less than 5% and not more than 40% by equivalent weight as active hydrogen group conversion on the basis of the total active hydrogen groups in the same compound. When the alicyclic diamine content is 1% by equivalent weight or more, the development of thixotropy is more remarkable and the fluid sagging (sag resistance) is more effectively prevented. And when the alicyclic diamine content is 50% by equivalent weight or less, the operation of curing polyurethane resins becomes easier.
(Chain Extender)
The chain extenders optionally used in curing agent (B) of the present invention are not limited to any specific types, and the types used in the preparation of conventional polyurethane resin compositions are applicable. These chain extenders include, for example, aromatic diamines such as 3,3xe2x80x2-dichloro-4,4xe2x80x2-diaminodiphenylmethane (MBOCA) and the polymeric compounds thereof, methylene dianiline (MDA) and the polymeric compounds thereof, diethyltoluene diamine (DETDA), and dimethylthiotoluene diamine.
(Catalyst)
The catalysts used in the reaction of a compound having an isocyanate group and an active hydrogen compound or in foaming of the present invention according to situations include, for example, organometallic catalysts including organotin compounds such as dibutyltin dilaurate, dioctyltin dimalate, stannous octoate and dibutyltin oxide, organotitunium compounds such as tetrabutyl titanate, organolead compounds such as lead naphthenate and lead octoate, and organobismuth compounds such as bismuth neodecanoate and bismuth octoate; and tertiary amines such as triethylenediamine, triethylamine, tetramethylenediamine, N-methylmorpholine, N,N-dimethylethanolamine and dimethylimidazoleamine. These catalysts can be used solely or in combination with one or more kinds. In addition, organic acids such as octanoic acid, oleic acid and o-toluic acid can also be used.
The amount of the above catalysts used may be properly set according to the intended physical properties of the desired products; generally the amount is 0.001 to 2 parts by mass per 100 parts by mass of the curing agent (B).
The two-component type polyurethane composition according to the present invention can be obtained by mixing the principal component (A) containing the compound having an isocyanate group and the curing agent (B) containing the compound having active hydrogen (an active hydrogen compound).
The method of mixing is not limited to any specific one. The principal component (A) and the curing agent (B) may be mixed in any desired manner taking into account the fact that isocyanate and active hydrogen reacts immediately after mixing to form a crosslinked structure, causing the development of thixotropy.
The mixing ratio of the principal component (A) to the curing agent (B) maybe properly set according to situations; generally and desirably the amount of the curing agent (B) mixed is 5 to 300 parts by mass per 100 parts by mass of the principal component (A), preferably 10 to 280 parts by mass per 100 parts by mass of the principal component (A).
The two-component type micro foamed polyurethane elastomer according to the present invention is obtained from the aforementioned principal component (A) containing a compound having an isocyanate group, the aforementioned curing agent (B) containing a compound having active hydrogen and a foaming agent, and both of the principal component (A), and the curing agent (B) contain substantially no thixotropic agent.
The total time immediately after the moment of mixing the principal component (A) and the curing agent (B) to the moment of the development of thixotropy is 2 seconds or shorter, preferably 1.5 seconds or shorter, and more preferably 1 second or shorter.
The slump of the mixture of the principal component and the curing agent is 3 mm or smaller, preferably 2 mm or smaller, more preferably 1 mm or smaller.
The above active hydrogen compounds have flash point of 60xc2x0 C. or higher, preferably 65xc2x0 C. or higher, and more preferably 70xc2x0 C. or higher.
When boiling the two-component type micro foamed polyurethane elastomer, which is obtained by curing the above mixture, in boiling water under atmospheric pressure for 60 minutes, change in mass of the above two-component type micro foamed polyurethane elastomer before and after the boiling is 0.6% or smaller by mass, preferably 0.55% or smaller by mass.
Desirably the two-component type micro foamed polyurethane elastomer according to the present invention has preferably break strength of not less than 0.5 MPa and not more than 30 MPa at xe2x88x9230xc2x0 C., more preferably not more than 25 MPa.
Desirably the two-component type micro foamed polyurethane elastomer according to the present invention has preferably elongation at break of not less than 20% and not more than 700% at xe2x88x9230xc2x0 C., more preferably not less than 50% and not more than 600%, particularly preferably not less than 50% and not more than 500%.
Though the total density is not restricted to any specific one, desirably the two-component type micro foamed polyurethane elastomer according to the present invention has preferably a total density of 100 to 900 kg/m3, more preferably 250 to 700 kg/m3. The term xe2x80x9ctotal densityxe2x80x9d used herein means the density of the two-component type micro foamed polyurethane elastomer including the surface layer portion and the inner center portion.
Desirably the average diameter of the cells of the two-component type micro foamed polyurethane elastomer according to the present invention is preferably 1 to 100 xcexcm, more preferably 5 to 70 xcexcm, and particularly preferably not more than 60 xcexcm. When the average diameter of the above cells is 100 xcexcm or smaller, since the tendency for the cell diameter to become coarse is restricted or prevented, two-component type micro foamed polyurethane elastomers having not only good touch, but enhanced mechanical properties can be obtained.
Desirably the two-component type micro foamed polyurethane elastomer according to the present invention has a constitutional unit having the following general formula [I]: 
wherein m, n represent an integer from 1 to 5 independently, preferably in the rate of not less than 0.001% and not more than 30% by mass, more preferably in the rate of not less than 0.005% and not more than 25% by mass.
The cells of the two-component type micro foamed polyurethane elastomer according to the present invention may be closed cells, open cells or the mixture thereof; however, those having a high closed cell rate are desirable. The closed cell rate is, for example, preferably 15% or higher, more preferably 30% or higher, and particularly preferably 60% or higher.
Preferably the two-component type micro foamed polyurethane elastomer has a skin layer (a layer having no cells) on its surface.
As a foaming agent, any of the chemical and physical foaming agents may be used as long as it can form a two-component type micro foamed polyurethane elastomer. However, water, carbon dioxide gas, liquefied carbon dioxide gas and the mixture thereof is preferable. These foaming agents can be used solely or in combination with one or more kinds.
(Chemical Foaming Agent)
As a chemical foaming agent, water is preferably used. Water can be used as a chemical foaming agent because it reacts with polyisocyanate to produce carbon dioxide gas. Generally and desirably, the amount of the chemical foaming agent, such as water, used is preferably not less than 0.05 parts and not more than to 5 parts by mass, more preferably not less than 0.1 part by mass, per 100 parts by mass of the total amount of the active hydrogen compounds contained in the curing agent (B), such as polyol and/or polyol with the polymer fine particles obtained by the radical polymerization of compounds having unsaturated bond dispersed therein and alicyclic diamine, etc.
(Physical Foaming Agent)
As a physical foaming agent, chlorofluorocarbons which have been developed so as to protect the global environment, hydroxychlorofluorocarbons (HCFC-134a etc.), hydrocarbons (cyclopentane etc.), carbon dioxide gas, liquefied carbon dioxide gas, and other foaming agents as foaming auxiliary are used solely or in combination with water. Of all the above agents, preferably used are carbon dioxide gas and liquefied carbon dioxide gas, and more preferably liquefied carbon dioxide gas, in view of the load on the global environment and of the fact that the density of polyurethane foam can be drastically changed by slightly changing its amount added.
Generally and desirably, the amount of the above physical foaming agents used is preferably not less than 0.01 part and not more than 3 parts by mass, more preferably not less than 0.05 part and not more than 2.5 parts by mass, and particularly preferably not less than 0.1 part and not more than 2.0 parts by mass per 100 parts by mass of the total amount of the active hydrogen compounds contained in the curing agent (B), such as polyol and/or polyol with the polymer fine particles obtained by the radical polymerization of compounds having unsaturated bond dispersed therein and alicyclic diamine, etc.
The two-component type micro foamed polyurethane elastomer according to the present invention can be produced by mixing the aforementioned principal component (A) containing a compound having an isocyanate group, curing agent (B) containing active hydrogen and foaming agent, and foaming the mixture thereof. In addition to the principal component (A), the curing agent (B) and the foaming agent, the two-component type micro foamed polyurethane elastomer may contain a chain extender, a urethane catalyst, a foam stabilizer, etc. according to situations.
Preferably mixing and agitation are performed using a low pressure or high pressure circulating foam molding machine preferably at the temperature range of 0 to 100xc2x0 C., and more preferably at the temperature range of 5 to 60xc2x0 C., though the molding temperature is not restricted to any specific one.
The same principal component (A) and curing agent (B) as used for producing the aforementioned two-component type polyurethane composition can be used as a principal component (A) and curing material (B) of the two-component type micro foamed polyurethane elastomer according to the present invention.
The polyurethane sealant according to the present invention is the sealant containing a two-component type polyurethane composition obtained from the principal component (A) containing the compound having an isocyanate group and the curing agent (B) containing the compound having active hydrogen, or the sealant containing a two-component type micro foamed polyurethane elastomer obtained from the principal component (A) containing the compound having an isocyanate group and the curing agent (B) containing the compound having active hydrogen and a foaming agent. It is obtained by mixing the principal component (A) and the curing agent (B) (and the foaming agent, in the case of a sealant containing the two-component type micro foamed polyurethane elastomer), and in addition, optionally additives such as filler, plasticizer, age resister, ultraviolet absorber, light stabilizer, antioxidant, coloring materials such as pigment and dye, and dispersant, according to situations.
Immediately after mixing, the compound having an isocyanate group and the compound having active hydrogen such as alicyclic diamine react with each other, form a crosslinked structure, causing the development of thixotropy. This sealant can be used as a foamed sealing material by the addition of a foam stabilizer and a foaming agent.
Although the sealant obtained in this manner may be applied to its object using a special applicator, generally it is directly applied to its object right after mixing.
As the agitating and mixing equipment for producing the above described polyurethane sealant according to the present invention, metering pumps such as gear pump, plunger pump in combination with a throttle valve can be used for pumping the raw materials and a mechanical rotary mixer, static mixer, etc. can be used for mixing, in addition to the hand-application using a conventional caulking gun.
Since the two-component type polyurethane composition according to the present invention promptly develops thixotropy, the efficiency of the operations such as agitation and mixing can be remarkably increased by the use of a high-pressure pump in combination with an impact type mixing gun.
In the production of the polyurethane sealant according to the present invention, the mixing ratio of the principal component (A) to the curing agent (B) can be properly set according to situations; however, generally and desirably the amount of the curing agent (B) used is not less than 5 parts and not more than 300 parts by weight, preferably not less than 10 parts and not more than 280 parts per 100 parts by weight of the principal component (A).
The two-component type polyurethane composition or the two-component type micro foamed polyurethane elastomer according to the present invention develops excellent thixotropy immediately after mixing a principal component containing a compound having an isocyanate group and a curing material containing a compound having active hydrogen (and the foaming agent, in the case of the two-component type micro foamed polyurethane elastomer), thereby enables its application under a variety of conditions such as mechanical-application and hand-application. In addition, it has excellent sag resistance and physical properties suitable for a sealing material. Because of the characteristics described above, the polyurethane sealant containing the above two-component type polyurethane composition or two-component type micro foamed polyurethane elastomer has excellent workability.